Maybe it's our caveman past, but people love holes in the ground. Whether it's digging in the sand at the beach, peering into an apocalyptic sinkhole, or perhaps even dabbling in spelunking, we are fascinated by the subterranean.
It's surprising then that it took so long for extreme caving to round into form as a serious pursuit of exploring the truly great natural spaces deep in the planet. Though the roots of extreme caving go back to the middle of the 20th century, it wasn't until several years into the 21st that the deepest known "supercave" was explored beyond 2,000 meters (6,561 feet) below the surface.
The discovery happened in 2004 in a supercave called Krubera, in the war-torn Republic of Georgia. It was one of the greatest exploratory accomplishments of this or any century, on par with climbing Mt. Everest, diving Challenger Deep, or landing on the moon. And yet, the story remains largely out of the limelight.
It's easy to see why. Caving is dark, dirty, unnerving work. When not squeezed into rib-cracking passageways or rappelling down 500-foot shafts, cavers are worrying about hypothermia, trying not to be soaked by roaring underground waterfalls, and staving off the psychological effects of prolonged exposure to absolute darkness.